This invention generally relates to the art of IC sockets and, particularly, to a terminal for use in such sockets, the terminal having different spring sections with different resiliencies. However, this concept is equally applicable for other types of electrical connecting devices.
An IC socket is used for performing burn-in tests of IC packages. In other words, an IC package is tested for a given number of hours at given, sometimes elevated temperatures to ensure that the IC package will not fail during normal operation. Such an IC socket typically includes a dielectric socket body or housing which mounts a plurality of terminals in respective terminal-receiving passages in the body. First contact ends of the terminals receive respective solder balls of a ball grid array of the IC package, for instance. The opposite ends of the terminals have tails which abuttingly engage circuit traces on a printed circuit board. Spring portions typically are provided intermediate the opposite contact ends of the terminals for applying linear contact pressure at the interconnections with the solder balls and the printed circuit board. A typical bum-in socket is shown in Japanese Unexamined Patent Publication No. HEISEI 6-203926 which shows terminals that have resiliently deformable linear spring strips. Another example is disclosed in Japanese Unexamined Patent Publication No. HEISEI 8-88063.
One of the problems in using spring-loaded terminals of the character described above is that compromises must be made in the amount of resiliency built into the terminals and yet have the terminals perform their intended purposes. In particular, high contact forces are desirable for applying pressures between the tail portions of the terminals and the circuit conductors on the printed circuit board to ensure good electrical contacts at these points. However, at the opposite ends of the terminals, lower contact forces are more desirable to ensure that the terminal contact ends do not damage the solder balls of the IC package. Consequently, compromises continuously are made in efforts to achieve sufficient contact forces at the tail ends of the terminals without damaging the solder balls at the opposite ends of the terminals. The present invention is directed to solving this problem by providing unique terminal configurations which are capable of applying different contact forces at opposite ends of the terminals.
An object, therefore, of the present invention is to provide an IC socket or other electrical connecting device with new and improved terminal configurations.
In the exemplary embodiment of the invention, an IC socket includes a dielectric socket body having a plurality of elongated terminal-receiving passages. A plurality of elongated terminals are received in the passages. At least some of the terminals each includes first and second opposite contact ends for longitudinal pressure engagement with appropriate contacts of a pair of electrical devices. A retention section is disposed intermediate the opposite contacts ends for fixing the terminal in its respective passage. A first spring section is disposed between the retention section and the first contact end. A second spring section is disposed between the retention section and the second contact end. The first and second spring sections are provided with different resiliencies for applying different contact pressures at the first and second contact ends, respectively.
As disclosed herein, the first and second spring sections are elongated and have sinuous configurations. The first and second spring sections generally have the same cross-dimensions. However, one spring section is longer than the other spring section to provide greater resiliency and, thereby, less contact pressure at the respective contact end of the terminal.
The IC socket is disclosed herein with a plurality of terminals having first contact ends recessed for receiving solder balls of an IC package. The second contact ends are in the form of tail portions for engaging circuit conductors on a printed circuit board. The first spring sections for the first contact ends at the solder balls have more resiliency than the second spring sections for the second contact ends at the printed circuit board. Therefore, greater contact forces are applied to the circuit conductors on the board than are applied to the solder balls.
Another feature of the invention is the construction of the socket body to include at least two parts on opposite sides of the retention sections of the terminals to sandwich the retention sections therebetween. The terminal-receiving passages extend through both body parts.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.